1. Field of the Invention
The present invention relates to pressure-sensitive adhesive tape rolls. Specifically, it relates to pressure-sensitive adhesive tape rolls which include a bobbin (core) and a double-sided pressure-sensitive adhesive tape helically wound around the bobbin, which double-sided pressure-sensitive adhesive tape includes a pressure-sensitive adhesive layer containing bubbles and/or hollow microspheres.
2. Description of the Related Art
Pressure-sensitive adhesive tapes including a thick pressure-sensitive adhesive layer, such as bubble-containing pressure-sensitive adhesive tapes, are used as pressure-sensitive adhesive tapes to be affixed to adherends having curved surface and/or uneven surface. Pressure-sensitive adhesive tapes are often commercially distributed as pressure-sensitive adhesive tape rolls which include a core and, wound therearound, a pressure-sensitive adhesive body bearing (temporarily being affixed to) a release liner (separator) on one or both sides thereof. Known procedures for winding such a pressure-sensitive adhesive tape around a core include “record winding” (disk winding) in which the pressure-sensitive adhesive tape is concentrically wound around the core at the same position to form a disk-like roll; and bobbin winding (cylindrical winding) in which the pressure-sensitive adhesive tape is traversed in a cross direction (width direction) and helically wound around the core (bobbin). Bubble-containing pressure-sensitive adhesive tapes and other pressure-sensitive adhesive tapes having a thick pressure-sensitive adhesive layer often employ bobbin winding, because if they are wound through disk winding, only short lengths (small meters) of them can be wound.
Such helically wound pressure-sensitive adhesive tape rolls, however, often suffer from blocking of the pressure-sensitive adhesive tape, because pressure caused typically by tape winding tension renders the pressure-sensitive adhesive layer to extend off the edge of the release liner to thereby cause blocking. As a possible solution to solve the blocking problem, there has been proposed a technique in which a release liner having a width larger than that of the body of a pressure-sensitive adhesive tape (pressure-sensitive adhesive body) so as to prevent blocking between lateral sides (side surfaces) of pressure-sensitive adhesive layers of adjacent portions of the pressure-sensitive adhesive tape.
Common release liners used for pressure-sensitive adhesive tape rolls include those having a substrate (carrier) and, arranged on a surface thereof, a releasably treated layer; and films made typically from a fluorine-containing polymer or non-polar polymer. A helically wound (bobbin-wound) pressure-sensitive adhesive tape roll, if employing such a common release liner, suffers from problems as follows. Specifically, the release liner may be accidentally or unintentionally peeled off due to its too good releasability typically during tape winding. In particular, when the release liner has a width larger than the width of the pressure-sensitive adhesive body so as to prevent the blocking typically in lateral sides of the pressure-sensitive adhesive layer, it often fails to give a pressure-sensitive adhesive tape roll which is tightly and systematically wound and has a good appearance. This is because, when the pressure-sensitive adhesive tape is wound, the release face of a portion of the release liner extending off the pressure-sensitive adhesive body (crosswise extending-off portion) comes in contact with the backside of the release liner of an adjacent turn of the pressure-sensitive adhesive tape, and this may cause collapse of the end regions during winding, cause dislocation (weaving) of the wound tape in a cross direction (width direction), or allow the air to enter in between adjacent portions of the pressure-sensitive adhesive tape. Additionally, the roll may become loose and wound down during unwinding of the pressure-sensitive adhesive tape.
To prevent weaving in a cross direction (looseness in winding) and other problems of such wound tapes, there is known a technique of using a release liner having a slightly tacky release face (see Japanese Unexamined Patent Application Publication (JP-A) No. 2008-12798). However, even this technique suffers from looseness in winding when adjacent portions of the pressure-sensitive adhesive tape overlap each other in a small width.